ES2573326T5 - System and procedure for reducing loads in a horizontal axis wind turbine that uses windward information - Google Patents

Description

DESCRIPTION

System and procedure for reducing loads in a horizontal axis wind turbine that uses windward information

The invention relates generally to wind turbines, and in particular to a system and method of reducing the load imbalance observed by the turbine components (rotor, drive train, tower) during normal operation.

Wind turbines are considered alternative sources of energy, environmentally friendly and relatively cheap. A wind turbine generator generally includes a wind rotor having a plurality of blades that transform wind energy into a rotational motion of a drive shaft, which in turn is used to drive a rotor of an electric generator to produce electrical energy. In modern wind power generation systems, the production of power from a plurality of wind turbine generators, comprising a "wind farm", is normally combined for transmission to a grid. The power output of a wind turbine generator generally increases with wind speed until a nominal power output is reached. Thereafter, energy production is usually constant at nominal value even with an increase in wind speed. This is generally achieved by regulating the action of the blade inclination in response to an increase in wind speed. With the increase in wind speed beyond nominal power output, the blades are generally tilted toward the boom (i.e., twisted to align more closely with the wind direction), thereby controlling the angular speed of the rotor. As a result, the speed of the generator and, consequently, the output of the generator can be kept relatively constant with increasing wind speeds.

In the event of sudden turbulent gusts, the wind speed, wind turbulence, and cross gradient can change dramatically in a relatively small time interval. Reducing rotor imbalance while keeping the power output of the wind turbine generator constant during these types of sudden turbulent bursts requires relatively rapid changes in the angle of blade pitch. However, there is usually a time lag between the appearance of a turbulent burst and the actual tilt of the blades based on the dynamics of the tilt control actuator and the inertia of the mechanical components. As a result, imbalances in generator loads and speed, and consequently, oscillations in turbine components, as well as power, can greatly increase during such turbulent bursts, and can reduce machine life and exceed the maximum prescribed level of energy production (also known as excessive speed limit) causing the generator to activate and, in certain cases, the wind turbine to stop. The overspeed limit generally has a protective function for the particular wind turbine generator and is based on fatigue considerations of mechanical components such as the tower, drive train, and others. On the other hand, sudden turbulent bursts can also dramatically increase bow-to-stern and side-to-side buckling moments in the tower due to the increased cross-gradient effect.

So far, load reduction has been addressed so far only by tilting the blades of the wind turbine while taking into account wind speed measurement upwind, to alleviate the impact of winds in turbulent gusts on the turbine. Consequently, rotor imbalance due to transverse gradient and wind turbulence has only been addressed by tilting the blades of the wind turbine in a reactive manner, based on the load on the tower due to the wind turbine input.

For example, various conventional techniques and devices are described in GB 2398841, US 6,320,272, US 7,025,567 and EP 1460266.

Accordingly, there is a need for a proactive mechanism to control the pitch of the blades of a wind turbine to compensate for rotor imbalance during normal operation by tilting the blades individually or asymmetrically, based not only on the wind speed, but also in the dynamics of wind turbulence and cross gradient in front of the rotor, determined before it reaches the rotor.

Thus, various aspects and embodiments of the present invention are provided defined by the appended claims.

Various features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which similar characters represent similar parts throughout the drawings, in which:

FIG. 1 illustrates a wind turbine generator in accordance with an embodiment of the present invention;

FIG. 2 illustrates a light detection and location (LIDAR) device and its associated measured wind speed components;

FIG. 3 illustrates a LIDAR mounted on a wind turbine hub and configured to measure a predetermined portion of a flat field in front of the hub;

FIG. 4 illustrates a front view of the LIDAR shown in FIG. 3;

FIG. 5 illustrates the functional elements of the wind turbine generator according to an embodiment of the present invention;

FIG. 6 is a system control diagram illustrating a control strategy for applying individual blade tilt control in accordance with one embodiment of the present invention; and

FIG. 7 is a flow chart illustrating an individual blade pitch control procedure in accordance with an embodiment of the present invention.

Although the figures of the drawings identified above establish alternative embodiments, other embodiments of the present invention are also contemplated, as indicated in the discussion. In all cases, this disclosure presents illustrated embodiments of the present invention by way of representation and not limitation. Numerous other modifications and embodiments may be devised by those skilled in the art that fall within the scope and spirit of the principles of this invention.

The following description presents a system and procedure according to one embodiment, for generating the windward information provided by a direct wind measurement sensor and using this information to determine the load that the rotor of a wind turbine generator will experience when the part wind turbine hits the turbine. Based on the estimated imbalance in the rotor, the blade angle changes so that the rotor sees the same uniform load across the rotor. The system and method can also be used to control the power output of a wind turbine generator during sudden changes in wind speed, cross gradient, and wind turbulence such as during a turbulent gust keeping the speed of the generator within the limit of excessive speed (or protection threshold) during such turbulent bursts, thus avoiding activation or shutdown of the wind turbine generator during turbulent wind turbine bursts. Embodiments of the present technique provide a control-oriented detection methodology for obtaining wind speed, wind turbulence, and cross-gradient information using wind-upwind measurement sensors and a set of control algorithms that process speed information, turbulence and windward gradient to generate individual blade tilt commands to individually tilt the blades of the wind turbine before a turbulent wind turbine blast occurs, thereby resulting in increased energy pickup wind and reduced dynamic loads on the structure of the wind turbine (rotor, drive train, tower, etc.). The system and method embodiments are described in detail below with general reference to FIG. 1-7.

Turbulent gust (or gust), as used herein, means a complex wind turbine regime that includes not only wind speed, but other wind dynamics such as, but not limited to, wind turbulence, gradient transverse and the like. Known gust models have considered wind speed only and do not include other wind dynamics.

Turning now to the drawings, FIG. 1 illustrates a wind turbine generator 10 in accordance with an embodiment of the present invention. Wind turbine generator 10 comprises a rotor 12 having a plurality of wind turbine blades 14, 16, 18 mounted on a hub 20. Wind turbine generator 10 also comprises a nacelle 22 which is mounted on top of a tower 24. The rotor 12 is drive coupled to an electric generator 32 as shown in FIG. 5, through a drive train housed inside the nacelle 22. Tower 24 exposes blades 14, 16, 18 to the wind (directionally represented by arrows 26), causing blades 14, 16, 18 to rotate around an axis 28. The blades 14, 16 and 18 transform the kinetic energy of the wind into a rotating torque, which is further transformed into electrical energy through the electrical generator housed inside the nacelle 22.

FIG. 2 is a simplified image illustrating a LIDAR 38 and its associated measured wind speed components that are measured within a predetermined cone angle and path (R) that can be appropriately selected to provide a desired precision of the measure, as well as an acceptable sensitivity. LIDAR 38 is described in more detail later in this document.

FIG. 3 illustrates a LIDAR 38 mounted on a wind turbine hub 20 and configured to measure wind speed components within a predetermined portion 44 of a flat field 40 in front of hub 20.

FIG. 4 illustrates a front view of the LIDAR 38 mounted on a wind turbine hub 20 depicted in FIG. 3. The cone angle (0) is shown in the x-y plane, where the z axis represents the axis of rotation of blades 14, 16, and 18 shown in FIG. one.

FIG. 5 is a block diagram of the main functional elements of the wind turbine generator 10 according to one embodiment. As illustrated, the blades 14, 16, 18 of the wind turbine generator 10 drive an electric generator 32 which is housed within the nacelle 22 shown in FIG. 1. The generator 10 The wind turbine further comprises a controller 30 configured to control the electrical energy production of the generator 32 based on the detected wind speed and at least other dynamics such as the cross gradient or the wind turbulence. The energy production of the electric generator 32 can be controlled through the preventive and individual control of the inclination of the blades 14,16 and 18 through the motors 34 of the blade inclination. By controlling the air gap torque of generator 32 through one or more power transformers 36, the power output of generator 32 can also be controlled simultaneously.

For low wind speeds, an increase in wind speed under certain wind turbulence and cross gradient conditions can cause an increase in the rotational speed of blades 14, 16 and 18, and, as a consequence, the production of generator electrical power 32. In certain embodiments, electrical energy production is allowed to increase with wind speed until a nominal level of energy production is reached. With further increases in wind speed, the power output of generator 32 remains substantially constant. This is accomplished by tilting one or more of the blades 14, 16, 18 towards the boom. In this analysis, tilt refers to the torsion of the wind turbine blade to change the angle of attack of the wind on the blade. The tilt towards the boom involves torsion of the blade so that the surface of the blade is aligned along the direction of wind speed 26 (ie, reducing the angle of attack). The inclination of a blade towards the boom leads to a decrease in the capture of wind energy by the blade. Consequently, with certain increases in wind speed, the blades progressively incline toward the boom, to maintain a substantially constant generator speed and, consequently, a constant production of energy by the generator.

As noted hereinabove, in the event of sudden turbulent gusts, wind speed, turbulence and / or cross gradient may increase or even decrease in a relatively small interval of time. In order to compensate the time span of the blade tilt motors 34 and maintain a uniform load across the rotor 20, and also maintain a constant power output from the wind turbine generator 10 during such turbulent sudden bursts, or at least a relatively smooth or controlled change in production, blades 14, 16, and 18 can be preventatively and individually tilted before a turbulent blast hits the turbine, thereby preventing turbine generator 10 wind reaches its speed limit (or low speed) when a gust appears. To apply this preventative tilt, wind dynamics that include but are not limited to wind speed, cross gradient, and wind turbulence are detected upwind of blades 14, 16, and 18 through one or more measurement sensors 38 of the wind to windward. Transverse gradient and wind turbulence information is determined from the wind speed information to provide a more complete and accurate wind dynamics profile for use by the proactive tilt control mechanism. In the illustrated embodiment, a sensor 38 includes a light detection and location device, also called a LIDAR. Referring again to FIG. 1, LIDAR 38 is a measurement radar that is configured to scan an annular zone around wind turbine generator 10 and measure wind speed based on the reflection and / or scattering of light transmitted by the aerosol LIDAR. The cone angle (0) and the path (R) of the LIDAR 38 can be appropriately selected to provide a desired measurement precision as well as acceptable sensitivity. In the illustrated embodiment, the LIDAR 38 is positioned on the hub 20 after which blades 14, 16 and 18 are mounted. In certain alternative embodiments, the LIDAR 38 may also be located around the base of tower 24 of the wind turbine.

In accordance with aspects of the present technique, the LIDAR 38 is configured to measure the wind speed ahead of at least a specific part, usually the most important sections of blades 14, 16 and 18 in terms of the contribution of those sections to the aerodynamic torque on the blades. These sections may include, for example, sections near the end of the blade. FIG. 3 illustrates such a measurement field 44. The points ahead of blades 14, 16 and 18 where the wind speed is measured by the LIDAR 38 are represented by a plane 40 in FIG. 3.

According to one embodiment, the potential load seen by the wind turbine 10 when reading the wind information in front of the structure will correlate the information to windward, which may include, without limitation, the wind speed, cross gradient and wind turbulence, by measuring the load provided by main flange sensors, blade root sensors, or main shaft sensors, and estimating when the new blade tilt adjustment needs to occur to compensate for this imbalance in the distance ahead of the wind turbine 10, where the wind speed and turbulence and the cross gradient have been recorded.

As illustrated in FIG. 5, the wind speed, cross gradient, and wind turbulence upwind ^{detected by LIDAR 38 is used by controller 30 to determine individual} blade tilt ^commands ( C i p ⁾ , where n is the number of blades of the wind turbine, and wherein the individual blade tilt commands are transmitted to each individual blade tilt motor within a plurality of blade tilt motors 34 to apply the actual change in the tilt of each blade 14, 16 and 18 by the blade tilt motors 34. The control mechanism applied by controller 30 is described more fully detail hereafter with reference to FIG. 6.

FIG. 6 is a schematic diagram illustrating an exemplary control mechanism 42 for applying preventive and / or individual blade tilt control in accordance with an embodiment of the present invention. The control mechanism 42 incorporates a feedback control system 45 and a direct power control system 46. The feedback control system 45 is configured to determine and feed back the sequentially corrected load values for each blade 14, 16, and 18 at summation point 47, based on the rotational speed C of blades 14, 16, and 18 of the wind turbine and also in the components F measured of the wind speed generated by the LIDAR 38 described previously herein. The locally measured load sensor data is then adjusted to asymmetrically apply a desired change in the rotational speed of each blade 14, 16, and 18 in block 50 and generate a corresponding output 48 indicative of

^{a required change in the angle} iCp) ^{of the blade pitch to achieve the required speed and} reduction in rotor imbalance. In block 52, the effect of changing the blade pitch based on a plurality of rotor and wind speed dynamics are separated to determine the actual changes in the active flow modifying devices employed to alter the aerodynamics of the blades. blades 14,16 and 18, and load values, respectively. The G ^b gain is based on turbulent wind dynamics that include without limitation wind speed, cross gradient, and wind turbulence, while the Gl gain is based on rotor speed dynamics. As will be understood, the output 48 of the feedback control system 45 is configured to cause a decrease in the blade tilt angle when the speed of the generator blades exceeds a reference speed and an increase in the angle of the blade tilt when the speed of the generator blades is less than the reference speed. Thus, under the normal operation of the wind turbine generator 10, the output 48 acts preventively and individually on each of the motors 34 of the blade inclination so that the imbalance of the rotor is reduced to a minimum and the total speed of the generator wind is maintained at a desired constant reference level.

Direct feed system 46 uses the wind speed (V ^w ) to windward information from the LIDAR 38 and generates an output 54 that is configured in combination with other turbulent wind dynamics such as, but not limited to, cross gradient and wind turbulence, to cause the blades to skew asymmetrically before a sudden change in wind turbulence, the amount of the slope being determined individually for each of the blades 14,16 and 18. The system 46 Direct feed incorporates a gain F in the wind speed (V ^w ) data at block 56 to produce output 54. Output 54 of the direct feed control system is summarized at node 58 with output 48 of system 45 of control of

^{feedback to produce the individual blade tilt commands,} ( C i p ^{). This gain F is} directly proportional to the expression Gb Gl-1, where Gb is based on the influence of wind speed, transverse gradient and wind turbulence on the blade dynamics, as previously indicated in this document. Thus, during a turbulent gust, the sudden change in wind speed is detected upwind of blades 14, 16 and 18, causing an increase in output 54 of direct feed system 46 and, consequently, a change in each shovel tilt command (C ^p ). This in turn causes the blade tilt motors 34 to skew the blades asymmetrically before the turbulent blast actually reaches the wind turbine generator 10. Thus, the technique ensures that the rotor imbalance caused by the cross gradient and wind turbulence is reduced and that the power output of the wind generator 10 is gradually reduced and that the speed of the generator does not exceed the excessive speed limit that could cause it to activate. In certain embodiments, the gain F may be further proportional to the detected wind speed, such that the stronger the turbulent gust, the faster the response of the

_{direct feeding system 46 to modify the blade pitch commands,} ( Cp). _A

Scale tilt gain 68 can further be added to the wind dynamics at output 62 to provide command modifications to activate the flow modification devices associated with each of blades 14, 16, and 18.

FIG. 7 is a flow chart illustrating an exemplary procedure 80 for compensating for rotor imbalance through a wind turbine due to wind turbulence and cross gradient and also for controlling the power output of a generator 10 wind turbine according to aspects of the present technique. Procedure 80 begins by scanning the windward wind field in front of the rotor represented in block 82. Block 82 can incorporate the use of a LIDAR 38 to scan the wind field ahead of the most important sections of blades 14 , 16, and 18 for aerodynamic torque to determine sudden changes, for example, in wind speed, cross gradient, and wind turbulence.

In block 83, wind speed, wind turbulence, and cross gradient are determined from the explored wind field information.

In block 84, the imbalance of the rotor induced by the wind field reaching the rotor is determined based on the above information on wind speed, wind turbulence and cross gradient.

In one embodiment, the windward sensor 38 determines the wind speed ahead of the turbine and determines what the load would be seen by the turbine components, in particular the rotor, when the wind reaches the turbine. Block 82 may incorporate a feedback control system as illustrated in FIG. 3 above. A control algorithm, as described above with reference to FIG. 6, determines a priori the blade angle at which each blade 14, 16 and 18 should be set for when the wind reaches the rotor, to compensate for any rotor imbalance, represented in block 84. A direct feed signal is generated. based on blade dynamics and changes in wind speed, cross gradient, and wind turbulence to windward. The blade tilt signal and the direct feed signal are then summed to preventively and individually determine the blade tilt commands as noted herein above with reference to FIG. 6. The blade tilt motors are driven in response to individual blade tilt commands, to effect preventive tilt of the individual blades before a sudden change in the dynamics of wind speed, cross gradient and / or wind turbulence.

One way to understand the potential load seen by the wind turbine 10 when reading the wind information in front of the structure is to correlate the information upwind with the measurement of the load provided by main flange sensors, root sensors of the blade or main shaft sensors, and estimate the time when the new adjustment of the blade inclination has to take place to compensate for this imbalance in the distance ahead of the turbine where the wind speed has been recorded.

Thus, the techniques described above facilitate the optimal use of wind dynamics information to windward to compensate for rotor imbalance and control fluctuations in the power output of the wind turbine generator during sudden changes in wind speed, gradient transverse and wind turbulence, while reducing dynamic loads on the tower structure. As will also be understood, the techniques described above can take the form of processes and apparatus applied by computer or controller to implement those processes. Aspects of the present technique may also be carried out in the form of instructions containing computer program codes collected on tangible media, such as floppy disks, CD-ROMs, hard drives, or any other computer-readable storage medium, in which, when the computer program code is loaded and executed by a computer or controller, the computer becomes an apparatus for practicing the invention. The techniques described can also be performed in the form of a computer program code or signal, for example, if it is stored in a storage medium, is loaded and / or executed by a computer or controller, or is transmitted through some means transmission, such as wires or electrical wiring, through fiber optics, or by means of electromagnetic radiation, in which, when the computer program code is loaded and executed by a computer, the computer becomes an apparatus for putting in practice the invention. When applied to a general-purpose microprocessor, the computer program code segments configure the microprocessor to create specific logic circuits.

Although only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It should be understood, therefore, that the appended claims are intended to cover all modifications and changes that fall within the scope of the invention.

Claims (4)

1. A wind turbine (10), comprising: a plurality of blades (14, 16, 18) mounted on a rotor (12); at least one windward to windward dynamics sensor (38) configured to detect a plurality of transient windward to windward dynamics at a desired distance from the wind turbine generator (10) in a direction of the wind moving toward the generator ( 10) wind turbine, in which at least one transient wind dynamics to windward is different from the wind speed and includes the transverse gradient and / or wind turbulence; a direct feed control system (46) configured to determine a direct feed signal in response to a change in detected transient windward wind dynamics and coupling of the direct feed signal to the tilt command signal the shovel to preventively and asymmetrically obtain command signals of the individual inclination of the shovel; and a tilt control system (42) configured to asymmetrically control the tilt of a plurality of blades (14, 16, 18) of the wind turbine generator (10) based on wind speed upwind and a change in the plurality of transient wind dynamics detected prior to a change in transient wind dynamics on the plurality of blades (14, 16, 18) using the direct feed signal to determine a signal from the preventive blade tilt command to asymmetrically controlling the inclination of the plurality of wind turbine blades (14, 16, 18) before a change in transient wind dynamics on the wind turbine blades (14, 16, 18) so that the rotor imbalance due to transverse gradient and / or wind turbulence it is reduced through the rotor (12), wherein the at least one windward wind dynamics sensor (38) comprises a light detection and location device. further comprising a feedback control system (45) configured to determine a bucket tilt command signal based on a difference between a local load sensor signal and a corrected load value. wherein the feedback control system (45) is configured to adjust the locally measured load sensor data to asymmetrically implement a desired change in the rotational speed of each blade (14, 16, 18) and generate an output ( 48) corresponding indicative of a required change in the angle of inclination of the blades, in which the direct feed system (46) uses the information from the wind dynamics sensor (38) to windward and generates an output (54) that is configured to make the blades tilt, asymmetrically, the amount of tilt being determined individually for each shovel (14, 16, 18), wherein the direct feed (46) system incorporates a gain (F) in the wind speed data received from the windward wind dynamics sensor (38) to produce an output (54) which is summarized in a knot with the output (48) of the feedback control system (45) to produce the individual blade tilt commands where the gain (F) incorporated by the direct feed system (46) is directly proportional to an expression GbGl-1, where Gb is based on transient wind dynamics to windward, while the gain Gl is based in the dynamics of rotor speed. The wind turbine (10) of claim 1, wherein the tilt control system (42) comprises means for controlling the sampling of transient wind dynamics to windward at a desired distance from the turbine generator (10) wind in one direction of the wind. The wind turbine (10) of any preceding claim, wherein the tilt control system (42) further comprises means configured to use the direct feed signal to determine a tilt command signal from the preventive blade to control the inclination of no more than a single wind turbine blade (14, 16, 18) prior to a change in transient wind dynamics on the wind turbine blade (14, 16, 18). A method of controlling the imbalance of the rotor (12) of the wind turbine generator (10) of any preceding claim in response to a predicted change in wind dynamics, comprising: detecting a plurality of wind to windward dynamics at a desired distance from at least one wind turbine blade (14, 16, 18) in a direction of the wind going to the wind turbine generator (10), wherein at least a wind dynamic is different from the wind speed and includes the cross gradient and / or the turbulence of the wind; and asymmetrically controlling the inclination of at least one blade (14, 16, 18) of the wind turbine generator (10) based on the wind speed upwind and a change in the plurality of wind dynamics detected before a change in the wind dynamics in at least one blade (14, 16, 18), such that the imbalance of the rotor (12) due to the transverse gradient and / or the turbulence of the wind is reduced through the rotor (12).